The use of particles to abrade contacted surface areas is well known. Particles can moved by kinetic energy to remove material from other surfaces, as by buffing, polishing, tumbling and by directed flow of particles in a carrier media. The best known large scale example of directed flow of particles in a carrier media is sand blasting. Sand blasting is done using industrial scale equipment, consuming bags of generally screened, but non-uniform size particles. A high air pressure is used to spray the sand on the surface to be impacted, thereby causing abrasion of the surface and with higher pressure cause actual cutting of the material
For smaller sized applications, the sand size is more tightly uniform. For indoor use, and for reasons of cleanliness and sanitation, the collection of spent sand must also be accommodated. In U.S. Pat. No. 5,037,432, a hand held device which facilitates the collection of spent sand is illustrated. In this device it is stated as an essential element, that the flow of sand impinge upon the surface to be abraded at an inclined angle. In fact, the device of this patent is designed primarily toward the circularity of the return path of the spent sand, and provides an opening for abrasion as part of the circular path of travel of the abrading material. Abrasion is caused by having the abrading material pass laterally by the surface of material to be abraded and by a sloughing action removes material. The material is removed in a non-linear fashion with most material removed at the upstream end of exposure of the surface to be abraded in the path of circular flow of the abrading material. The abrasion of the material surface downstream of the initial contact is caused by tumbling of the media and further mixed sloughing. Because of the shallow angle of attack, at least half or more of the kinetic energy in the particles is used to move them along in a tumbling fashion end over end, meaning that less than half of the kinetic energy of the particles can be applied to abrade the target surface. These design characteristics makes the tool inefficient and limits its use for various applications. Further, such inefficient use translates into the wasting use of abrading material. Three to five times as much abrading material will be used to remove a given amount of material to be removed as would otherwise be necessary.
Control of the flow of the abrasion material is critical for small scale applications and especially where delicate work is to be performed. As such the control system should be able to produce a smooth and even control of abrasive force to be applied. The tool should facilitate accurate control by allowing an even and proportional application of force. Removal of abraded material should occur through impact, and not inefficient lateral sloughing and trough digging.
Further, because the stream of flowing particles abrades the surface at an angle, a sharp focus cannot be achieved. Etch writing or other closely tolleranced work cannot be performed both due to the spreading of the stream of abrasive media, as well as due to uneven application of energy to the abraded surface.
Another problem with conventional abrasion devices is the creation of pollution in that the abraded material is not always safely collected and isolated. For example, industrial paint stripping operations with lead based paint in which the removed material is allowed to settle like ordinary dirt can provide ground contamination both around the plant and at the land fill. In addition, where the abrasive material and removed material are not collected for safe disposal, workers are exposed to airborne contaminants.
Filtering the abraded waste material along with the particulates of the abrasive material presents an especial problem. In most cases the size of the abraded waste material will vary in size from flakes larger than the abrasive material, to a fine powder much smaller than the abrasive material. Collection must be had with extreme filtration of the most fine particles, but also without having to provide an expanded surface filter which must be changed continually over a series of short periods of time. Collection of the spent abrasive material may also result in its being treated to remove the abraded material and then recycled, if such is economically feasible.
Control and isolation of abraded material is even more of an issue in medical applications where the abrasive material is used to remove skin in medical procedures involving active acne, acne scars, blackheads, tattoos, or other skin conditions such as psoriasis and exema. Skin removal must be done gently to avoid cutting the skin and abrading past the point where blood vessels are encountered. Skin as abraded material should be isolated and prevented from re-use without having formal sterilization and re-processing. All abraded skin should be treated as contaminated medical waste and should be collected into a waste collection space which includes a sealed container with back flow protection and ultimately formal destruction and proper disposal.